Add package.xml to allow build in catkin workspace

package.xml

+<?xml version="1.0"?>
+<package format="2">
+  <name>example-robot-data</name>
+  <version>2.3.0</version>
+  <description>Set of robot URDFs for benchmarking and developed examples.</description>
+  <!-- The maintainer listed here is for the ROS release to receive emails for the buildfarm. 
+  Please check the repository URL for project maintainer. -->
+  <maintainer email="wolfgang.merkt@ed.ac.uk">Wolfgang Merkt</maintainer>
+  <license>BSD</license>
+
+  <url type="repository">https://gepgitlab.laas.fr/gepetto/example-robot-data.git</url>
+
+  <build_depend>git</build_depend>
+  <depend>python</depend>
+  <depend>python-numpy</depend>
+  <depend>boost</depend>
+  <depend>pinocchio</depend>
+
+  <buildtool_depend>cmake</buildtool_depend>
+  <export>
+    <build_type>cmake</build_type>
+  </export>
+</package>